The present invention generally pertains to a galvanic battery with band-shaped positive and negative electrodes, and an intermediate band-shaped separator, which are helically wound to develop an electrode structure for mounting within a cylindrical housing having a cell pole which is insulated and sealed against the housing, and a connecting element which electrically bridges the gap between the cell pole and the edge of the corresponding band electrode.
The present invention is preferably applicable to lithium cells, but is also applicable to Ni/Cd storage batteries in round cell form (e.g., with wound sintered-foil electrodes). In winding cells of this type, the electrode band of one polarity is generally made somewhat longer than the electrode band of the other polarity so that the former can develop the outermost end of the spiral winding and can be brought into direct contact with the inner wall of the cell housing. As a rule, the outermost spiral winding constitutes the negative electrode, and consequently, the cell housing serves as the negative pole for the assembled cell.
In contrast, the remaining electrode band (of the other polarity) must be connected to the corresponding cell pole, which generally takes the form of a metal button recessed in the cell cover and which is insulated from the cover, a flanged cap, or a metallic cell cover. In either case, a connecting element is required to bridge the distance between the cell pole and the corresponding electrode. For example, as disclosed in DE-PS 30 14 435, a coil spring can be used as this connecting element, to place the collector rod of a wound lithium electrode in contact with a metallic housing cover (developing a negative cell pole).
Yet another approach is to weld a lug to an exposed edge (active mass removed) of the band electrode. In the course of assembling such a cell, this lug must be positioned for connection (e.g., by resistance welding) to the corresponding cell pole. However, with even the shortest distance between the cell pole and the connecting lug, a flexible intermediate connection cannot be used due to limitations of the welding process, and in assembly of the cell, complicating manufacture. The dense alkaline cell disclosed in U.S. Pat. No. 3,579,387 is one example of this.
Conductor lugs of this general type also tend to interfere with winding of the electrode, and to reduce the capacity of the winding machine. What is more, the conductor lug which is then projecting upwardly from the cell housing tends to interfere with electrolyte dosing under vacuum since the cell is then often poorly sealed. In addition, such conductor lugs can tend to inhibit prevailing automated production processes.
In connection with the manufacture of wound lithium cells, there are added problems since in such case the conductor lug is preferably rather long, to allow for the fan-fold which is preferred, and because the welding of the conductor lug must be carried out in an inert (argon) environment.